Epoxy resin systems are generally relatively brittle and do not exhibit as much toughness as would be desired. This restricts their usefulness to instances when such brittleness and lack of toughness can be tolerated. Improved toughness would be advantageous, for example, in epoxy adhesives and coatings and in composites of glass and/or graphite fibers embedded in cured epoxy resins such as are used for aircraft bodies and parts.
For some requirements, such as for filament winding, a liquid epoxy compound is coated on filaments as they are being wound and is cured in place. Another use for epoxy resin systems is wherein a liquid epoxy compound is flowed around a pack or bundle of interwoven or parallel glass or graphite fibers and cured. In such situations the viscosity of the liquid epoxy compound must not be too high. Unfortunately, the viscosity of the liquid epoxy compound will generally be rather high for such uses. Also, because the liquid epoxy compound is polymerizing as it is being coated on the filament or flowed about the fibers it is very difficult to control the viscosity to be as low as is necessary throughout the entire operation. The prior art has added such compounds as styrene to the liquid epoxy compound in order to lower its viscosity. This, however, creates another problem in that a two phase system normally results with polystyrene, which results from simultaneous heat catalyzed vinyl polymerization of the styrene, dispersed in the resulting cured epoxy resin.
A practical consideration with the utilization of epoxy resin systems is that the epoxy compounds from which they are formed are generally quite expensive. Accordingly, it would be desirable to provide inexpensive compositions which could be incorporated in epoxy resin systems and serve as diluents without adversely effecting the properties of such systems.
The present invention is directed to solving one or more of the problems as set forth above.